Phylogeny and taxonomy of Cinnamomum (Lauraceae)

Abstract Taxonomy of Cinnamomum Schaeff. of Lauraceae remains problematic because recent phylogenetic studies have suggested that this genus is not monophyletic. In this study, we assembled three sequence matrices including plastomes (datamatrix I), nrITS sequences alone (datamatrix II), and nrITS plus plastid psbA‐trnH sequences (datamatrix III) of the Cinnamomum‐Ocotea complex of Lauraceae and conducted a new phylogenetic study with thusfar the most extensive species sampling of the Cinnamomum‐Ocotea group. We determined that the Old World Cinnamomum is diphyletic: sect. Camphora Meisn. is sister to Sassafras J.Presl and sect. Cinnamomum is sister to the African Kuloa Trofimov & Rohwer. A recent study indicated that characters of leaf micromorphological anatomy can define the two clades: one possessing reticulate periclinal and the other having non‐reticulate periclinal walls. As result, we divided the genus Cinnamomum of Lauraceae into two genera, i.e., Cinnamomum and Camphora Fabr. The generic name Cinnamomum is retained for those species mainly having reticulate periclinal epidermal cell walls, inconspicuous non‐perulate terminal buds and usually tripliveined leaves; the oldest generic name, Camphora, is applied to the second group which contains those species mainly possessing non‐reticulate periclinal epidermal cell walls, prominent perulate terminal buds and pinnately‐veined leaves. A census of the species and their type specimens listed under Cinnamomum in Asia resulted in the transfer of 18 species to Camphora, including 15 new combinations.

is probably the most difficult one of the family Lauraceae because early researchers usually studied materials including detached leaves of uncertain origin that were mostly picked from immature The genus Cinnamomum was formerly considered to contain 350 species that are amphi-Pacific (Lorea-Hernández, 1996;Rohwer, 1993;van der Werff, 2001). Recent phylogenetic and taxonomic studies have transferred the American species to Aiouea (Rohde et al., 2017), so the remaining Old World Cinnnamomum now contains 247 species (https://powo.scien ce.kew.org/taxon/ urn:lsid:ipni.org:names :32826 2-2#children). Species of Cinnamomum are usually subdivided into two groups: one group including species having alternate and pinnately veined leaves, domatia present in the axils of lateral veins and middle veins, and perulate terminal buds ( Figure 1); and the other group containing species possessing opposite/subopposite and tripliveined leaves lacking domatia in the axils of lateral veins, and non-perulate terminal buds (Figure 2;Lorea-Hernández, 1996;Huang et al., 2016). The two groups are normally ranked as two sections, i.e. sect. Camphora Meisn. (syn.: sect. Malabathrum Meisn.) and Cinnamomum (Hooker, 1886;Kostermans, 1986;Li et al., 1982;Lorea-Hernández, 1996;Meissner, 1864) Nees (1831Nees ( , 1836, however, separated the two groups into two genera: Camphora and Cinnamomum. Besides the macromorphological differences, the two groups are also different in characters of the upper leaf epidermis: (1) the cell shape is regular in sect. Camphora, but irregular in sect. Cinnamomum; (2) the anticlinal wall is straight or nearly so in sect. Camphora, but sinuous in sect. Cinnamomum; and (3) the periclinal wall is smooth in sect.
Relationships of the Cinnamomum-Ocotea complex have not been resolved. Trofimov and Huang et al. (2016) suggested that sect. Cinnamomum is sister to the Neotropical clade, whereas Rohde et al. (2017) indicated that sect. Camphora is sister to the Neotropical clade. Trofimov and Rohwer (2020) suggested that the Old World Cinnamomum is diphyletic or paraphyletic as well, with sect. Cinnamomum sister to Kuloa Trofimov & Rohwer and sect. Camphora sister to Sassafras J. Presl. Other recent studies considered the genus Cinnamomum as paraphyletic with regard to Sassafras Song et al., 2020;Trofimov et al., 2022), which may be attributable to sampling bias, none of them included Kuloa. The phylogeny of Cinnamomum is thus not well resolved, so further phylogenetic studies are necessary to determine the monophyly of Cinnamomum, and the genus should be further subdivided if confirmed to be polyphyletic. As a result, our target here is to (1) reconstruct a resolved phylogeny of the Cinnamomum-Ocotea complex with a broad sampling of the genus Cinnamomum using separate and concatenated sequence matrices including plastomes, nrITS and psbA-trnH sequences, and (2) conduct a new synoptic taxonomy of sect. Camphora if the polyphyly of the genus is confirmed.  (Katoh et al., 2017) using Auto and Localpair model for CPG and the two markers respectively, then adjusted and edited manually in BioEdit (Hall, 1999). Ambiguously aligned fragments of CPG were removed with Gblocks using default setting (Talavera & Castresana, 2007) and gap sites of nrITS and psbA-trnH sequences were deleted with trimAl using "-automated1" (Capella et al., 2009). Totally, we assembled three matrices: complete plastome sequences (datamatrix I), nrITS (datamatrix II), and a datamatrix including nrITS and psbA-trnH (datamatrix III). The two markers of datamatrix III were concatenated using PhyloSuite (Zhang et al., 2020). A best-fit or partition model of all matrices was computed with ModelFinder (Kalyaanamoorthy et al., 2017). For phylogenetic studies, maximum likelihood (ML) analyses were conducted in IQ-TREE (Nguyen et al., 2014), bootstrap values were obtained using Ultrafast Bootstrap for 5000 and 1000 times for the datamatrix I and other two datamatrices separately (Minh et al., 2013); Bayesian inferences (BI) were conducted in MrBayes (Ronquist et al., 2012) with the following parameters:
As a result, we transfer those species usually with alternate and pin-

| Distribution
Tropical to subtropical Asia.

| Remarks
Several species were placed previously into sect. Camphora because they have seemingly pinnately veined leaves, e.g., Cinnamomum chago, C. longipetiolatum, and C. saxatile, but our molecular study suggests that these species belong to Cinnamomum (Figures 3 and   4). Similarly, Gang et al. (2021) also suggested that C. saxatile belongs to the former sect. Cinnamomum as it possesses reticulate periclinal walls. Sun and Zhao (1991) noted that leaves of C. chago are pinnately veined with 7-9 pairs of lateral veins, the proximal pair starting from the base of leaf blade and appearing subtriveined, suggesting that the leaf venation of the species is probably triveined. However, leaf micromorphology should be examined for these three species (and other Cinnamomum-like taxa, such as Temmodaphne thailandica) before their taxonomic position can be confirmed. Therefore, we retain these species in Cinnamomum for now, pending further study.

| Distribution
Tropical to subtropical Asia, but mostly distributed in the Northern Hemisphere ( there is no species with pinnately veined leaves in southern India (Kostermans, 1985).    (Li et al., 2008).
However, this species markedly differs from the latter in the purplish color of its branchlets, petioles, pedicel, and peduncles. We thus treat it as a separate species here. isosyntype: K000350905). When Kostermans (1970) transferred the species to Cinnamomum, he wrote "Typus: Forrest 16021 (E), syntypus: Forrest 13667 (E)." This may be interpreted as lectotypification in the sense of the fruiting specimen E00123606, even though E00123605 is the better flowering material.

ACK N OWLED G M ENTS
We are thankful to Jens G. Rohwer for his kind help on typification of the names, and constructive suggestions on an earlier version of this manuscript; we are also grateful to two anonymous

CO N FLI C T O F I NTE R E S T
The authors declare that there is no conflict of interest.

DATA AVA I L A B I L I T Y S TAT E M E N T
All data used in the study are included in this paper.